Variable density window



4 05am nuum E. H. LAND Feb. 23, 1943.

VARIABLE DENSITY WINDOW Original Filed NOV. 10, 1938 FIG. 3

Search KOOY Patented Feb. 23, 1943 VARIABLE DENSITY WINDOW Edwin H. Land, Cambridge, Mass., assignor to Polaroid Corporation, Dover, Del., a corporation of Delaware Original application November 10, 1938, Serial No. 239,796. Divided and this application November 8, 1940, Serial No. 364,878

3 Claims. (Cl. 88-65) This invention relates to variable density occasions. This is particularly true in railroad windows. vehicles, where the upper portion of the window This application: is a division of my co-pending application, Serial No. 239,796, filed November almost invariably remains covered by an opaque curtain or screen, only the lower portion being 10, 1938, which latter application has issued as 5 usefully employed. So also in dwellings it is Patent 2,237,566, April 8, 1941. frequently customary to leave a shade or curtain An object of the invention i to provide a drawn over a considerable portion of the window variable density window comprising a plurality area or to hang drapes or curtains or similar of overlying light-polarizing elements and means light-obstruction element so as to block apassociated therewith for controlling at will the preciable portions of the window areas. amount of light transmitted thereby. The control of light intensity at the windows A further object of the invention is to provide has thus been accomplished frequently by a rea variable density window of the character strictlon of the window aperture usefully emdescribed wherein one of the light-polarizing eleployed. In other cases it has been accomplished ments is fixedly positioned and the other element by drawing across the window a curtain, screen movable with respect thereto. or the like which completely destroys the trans- A still further object of the invention is to parency of the window unit and makes it imposprovide such a window wherein the movable sible for a person positioned within the vehicle, element is rotatably mounted. dwelling or the like to see through the window.

Other objects of the invention will in part be It is an object of the pr invention o pr obvious and will in part appear hereinafter. vide a variable density window of a character The invention accordingly comprises an article such that the intensity of the light tted of manufacture possessing the features, propthereby may be controlled accurately from a erties and the relation of elements which will be predetermined maximum to complete cut-off, if exemplified in the article hereinafter described 35 desired, without obstructing the clarity of the and the scope of the application of which will be image transmitted by the window, at least until indicated in the claims, the point of substantially complete cut-off is For a fuller understanding of the nature and reached. This may be accomplished by providobjects of the invention reference should be had me a pa of overlying light-polarizing e e ents to the following detailed description taken in each preferably substantially the size of the full connection with the accompanying drawing, in Window aperture and by the provision of means which: for moving a transparent element, for example Figure l is a view partially in perspective and one of the polarizing elements with respect to partially in section of a device embodying one the other of the elements so that the intensity form of the invention; of the light transmitted by the combination of Fig. 2 is a diagrammatic view in front elevation elements may be controlled. of one of the elements of a window unit shown In the preferred form of the invention one of i Fig, 1; and the elements is fixedly mounted and this is pref- Fig, 3 is a view in section enlarged and to some erably the outer element which may be provided extent distorted of a portion of the device shown With a fra e or mounting means o a character in Fig. 2 taken along the line 3--3. to hold the element rigidly in position and to Heretofore, when it has been necessary or deprevent the infiltration of dust or air about the sirable to reduce the intensity of light transedges of the element. Such a permanent, rigid mitted by a window in a dwelling, vehicle or the ou t ng is preferred in cases in which the like. the desired result has been accomplished by window of the present invention is to be emdrawing across the window a supplemental ployed in connection with air-conditioning means translucent or opaque substance such as a shade, as for example where the window of the present curtain or blind. Speaking generally this has invention is to be employed in air-conditioned resulted in an impairment or complete destrucrailroad trains, dwellings and the like, Wh tion of the clarity of the image visible through the window of the present invention is to be emthe window or at least through those portions of ployed under conditions in which it may b the window over which the shade or blind has sirable at times to open the window and admit been drawn. As a result it has been found that air, the mounting means may preferably be of the frequently a considerable portion of the window usual kind to permit any desired opening of the area performs no useful function, except on rare window element.

The other element of the window of the present invention may be mounted for relative motion with respect to the first element. In the simplest form of the invention one element may be rotatably mounted with respect to the other element. In such a structure, when the'polarizing axes of the two polarizing elements are parallel a maximum of light is transmitted by the window, and this may be progressively decreased by a rotation of the rotatable element until, when the polarizing axes of the elements are crossed, substantially complete cut-off is obtained. The rotation of one element with respect to the other doe not destroy the clarity of the image transmitted by the window as a whole. So long as any light is transmitted the objects outside the window may be visible.

Where one of the polarizing elements of the window is rotatably mounted with respect to the other element, it is highly desirable that access be provided to the space between the two elements in order that theirsurface may be cleaned and the efficiency of the window unit not impaired by an accumulation of dust. To this end the rotatable unit, or if desired the non-rotatable unit, may be pivotally or removably mounted so that it may be swung away from or removed from the other element and access provided to the space between the elements.

It will be apparent that a preferred structure contemplates the provision of surfaces of relatively large areas, as the intensity of light transmitted through the entire window should preferably vary simultaneously over all portions of the window area. This implies the use of light-polarizing material of large surface area. Such material is commercially available in the form of a variety of types of light-polarizing films sold under the trade name Polaroid. One type of such material comprises a suspension of polarizing particles in a light-transmit ting medium, the particles being oriented to substantial parallelism and being so distributed throughout the medium as to impart substantially uniform polarization to a transmitted beam. A preferred form of such material for use in the present invention is a high concentration of polarizing crystals such as crystals of iodosulphate of quinine or iodosulphate of cinchonidine in a very thin film or layer of a transparent plastic, preferably a material such as that sold under the trade name Vinal or Vinylite XYSG. Films of this material of less thickness than .0003 of an inch have been found to be excellent polarizers and are now available in areas at least as great as any desired for use in the present invention.

It may be desirable to employ films or sheets of the above type laminated to or between sheets of glass or other rigid light-transmitting supporting media, and the use of such polarizing means is preferred. It is to be understood, however, that any other light-polarizing elements of large area, or adapted to be assembled to form large areas, may be employed in the present invention. It will be apparent that for satisfactory results the sheets or films of polarizing material employed should be relatively thin and highly efficient and if it is necessary to piece out the area by lamination or by overlapping smaller areas of polarizers the materials employed should be of a character such that large areas may be produced without the appearance of unsightly overlaps.

One form of the invention is shown in Figs. 1,

2 and 3. In Fig. 1, l0 represents generally the frame or body of the vehicle, dwelling or the like in which the windows of the present invention are positioned. The specific form shown in Fig. 1 is one adapted for use in connection with railroad trains and more particularly trains designed to be employed with suitable air-conditioning apparatus. The outer element I! of the window may be permanently mounted as for example at |4 in the vehicle frame. Upon the inner face, preferably, of this window element there may be a polarizing layer l6, which may take the form of a thin film such athose previously described. This film or layer may be bonded to a supporting glass plate and may fill the entire window aperture. It may be so mounted that its transmission axis, indicated generally as at l8, may be positioned in any desirable manner. If, for example, it is desired that the outer window act to block glare reflected from horizontal surfaces it should be so positioned that the layer blocks light vibrating in a horizontal direction, that is, with its transmission axis perpendicular to the horizontal.

The inner window element n may comprise similarly a sheet of glass having its inner face coated with a similar light-polarizing layer 22.

The polarizing axis of this layer may be indicated generally by the arrow 24. Either of the polarizing layers 16 and 22 may be covered by a waterproofing varnish or cement 26, or in any other manner, for the protection of the polarizing film. This is not necessary, however, for if the polarizing films or layers are on the inner faces of supporting glass plates, they will be protected during use by the plates themselves.

As shown in Figs. 1 and 2, the innermost window element 20 is preferably mounted in a frame 30 hingedly aflixed as at 32 to the main body of the vehicle. The frame 30 may be provided with suitable latch means 34 engaging the main body of the vehicle and holding the window element normally in closed position. When it is desired to clean the surfaces of the polarizing films or coatings, the latch 34 may be opened and the window 20 swung inwardly, permitting free access to the inner surfaces of the two window-pane elements.

One of the window elements, and preferably the innermost element, is mounted for rotation within its frame so that the polarizing axis 24 of the element may be rotated through at least an angle of As shown in Fig. 2, this may be accomplished by providing a rack or gear 40 on the rim of the window element 20 and providing a meshing gear 42 actuated by the crank 44, mounted on the frame 30. Rotation of the crank 44 will cause a rotation of the window element 20 within its frame. The relative position of the polarizing axis of the film 22 with respect to that of the film l6 may thus be controlled so as to permit any desired amount of light to traverse the window as a whole from a predetermined maximum, when the polarizing axes are parallel, to a predetermined minimum when the axes are crossed.

It will be understood that the above window may be actuated by motor means (not shown) remotely controlled in any suitable way. For example, all the windows of a car or dwelling may be adapted to be simultaneously operated and the intensity of light transmitted accurately controlled from a central control station. All such modifications are to be deemed within the scope of the invention.

Since certain changes may be made in the above article and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all the generic and specific features of the invention herein described, and all statements of the scope of the invention which. as a matter of language, might be said to fall therebetween.

Having described my invention what I claim as new and desire to secure by Letters Patent is:

l. A variable density window for illumination purposes comprising, in combination, frame means' providing a window aperture of substantial area, a sheet-like light-polarizing element of substantially the same area as said aperture, means for mounting said element within said frame, frame means providing a second window aperture of subsl'antially the same area as said first named aperture, a second sheet-like lightpolarizing element of substantially the same area as said first named polarizing element, means for rotatably mounting said second polarizing element within said second named frame means, means for rotating said rotatably mounted element within said frame means, and means including vertical weight-supporting elements within said first-named frame for removably mounting said second named frame means within said first named frame means with said polarizing elements in substantially parallel and superimposed relation.

2. A variable density window for illumination purposes comprising, in combination, frame CQHTCH nuum means providing a window aperture of substantial area, a sheet-like light-polarizing element of substantially the same area as said aperture. means for mounting said element within said frame, additional frame means positioned within said first named frame means and providing a second window aperture of substantially the same area as said first named aperture and in substantial registry therewith, a second sheet-like lightpolarizing element of substantially the same area as said first named polarizing element, means for rotatably mounting said second polarizing element within said second named frame means in substantially parallel relation with aid first named polarizing element, means for rotating said rotatably mounted element within said frame means, and means including vertical weight-supporting elements within said first-named frame means providing a pivotal connection between said second named frame means and aid first named frame means.

3. A structural assembly comprising frame means providing a multiplicity of adjacent window apertures of substantial area, a plurality of sheet-like light-polarizing elements of substantially the same area as each of said apertures, means for mounting one of said light-polarizing elements fixedly within said frame over each of said apertures, means for rotatably mounting anotherof said light-polarizing elements in said frame over each of said apertures in substantially parallel relation with the fixedly mounted lightpolarizing element thereadjacent, and means for separately and independently rotating each of said rotatably mounted light-polarizing elements with respect to the fixedly mounted light-polarizing elements thereadjacent.

EDWIN H. LAND. 

